| Abstract: | To investigate the effects of bilateralintrathoracic vagotomy on the establishment of continuous breathing andeffective gas exchange at birth, we studied 8 chronically instrumented, unanesthetized, sham-operated and 14 vagotomized newborn lambs after aspontaneous, unassisted vaginal delivery. Fetal lambs wereinstrumented in utero to record sleep states, diaphragmatic electromyogram, blood pressure, arterial pH, and blood-gas tensions. Six of eight sham-operated lambs established effective gas exchange within 10 min of birth, whereas 12 of 14 vagotomized animals developed respiratory acidosis and hypoxemia (P = 0.008). Breathing frequency in vagotomized newborns was significantlylower during the entire postnatal period compared with sham-operatednewborns. Vagotomized subjects also remained hypothermic during theentire postnatal period (P < 0.05).Bronchoalveolar lavage indicated an increased minimum surface tension,whereas lung histology showed perivascular edema and partialatelectasis in the vagotomized group. We conclude that stimulation ofbreathing and effective gas exchange are critically dependent on intactvagal nerves during the transition from fetal to neonatallife. |
